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Rao and colleagues [1] recently reported interesting differences between the esophageal mechanical properties of patients with noncardiac chest pain and those of healthy controls. However, controls were significantly younger than patients. In the same issue, Frobert and colleagues [2] report that whereas reflux episodes peak at the same time as noncardiac pain, reflux also peaks in a control group at the same time: This is a good demonstration that correlation does not mean causation.

In the case of esophageal planimetry, how much of the difference in mechanical properties and the lowering of sensation thresholds was due to age-related change alone? Were the patients who did not experience pain with planimetry younger than those who did? Is there a set of age-adjusted normal values for esophageal planimetry? Given the wide overlap of values between patients and controls in the study by Rao and colleagues, as was noted in Goyal's editorial [3], accounting for this simple difference in groups may make this new technique much more or less interesting.